1. Field of the Invention
The present invention generally relates to a liquid jetting device and a drive voltage correction method for individual drop, and more particularly to a liquid jetting device and a drive voltage correction method used for an ink jet printer to set uniform droplet from all nozzles, a manufacturing apparatus coating a liquid material, and the like.
2. Description of the Related Art
An ink jet printer is generally known as an image recording apparatus recording an image on a recording medium such as paper. A liquid jetting device for jetting ink is installed in an ink jet printer, and the liquid jetting device is equipped with a recording head to jet the ink from a plurality of nozzles, and a drive circuit to drive the recording head.
The recording head is equipped with a jetting energy generating element to each nozzle for jetting ink from each of the plurality of nozzles. As the jetting energy generating element, a heater element generating air bubbles by heat to jet the ink by the pressure of the generated air bubbles, an actuator jetting the ink by deforming to apply a pressure to the ink, and the like are known. Hereinafter, the actuator is exemplified to be described as the jetting energy generating element.
The actuator as the jetting energy generating element is connected to the drive circuit, and is configured to expand and shrink based on a drive signal inputted from the drive circuit for jetting the ink droplet from a nozzle. By the way, even if a drive signal of the same voltage value is applied to each nozzle, the deformation speeds and the deformation rates of the actuators are fluctuated owing to the individual differences of the nozzles, and the fluctuation has been an adverse effect of high-definition image recording as a result. There has been the same adverse effect also in the recording head adopting the heater element as the jetting energy generating element.
For settling the problem, in recent years, a liquid jetting device configured to measure a jetting speed and a jetting quantity to correct the fluctuation among them through drive voltage control based on the measured values has been developed (see, for example, JP-Tokukaihei-7-256884A and JP-Tokukai-2004-90621A). For example, the liquid jetting device (an ink jet printer) described in JP-Tokukaihei-7-256884A is provided with a jetting speed measuring device measuring the jetting speed of the ink droplet from the nozzle, and is configured to correct the voltage value of the drive signal by getting the feedback of a measured value of the jetting speed measuring device. On the other hand, the liquid jetting device described in JP-Tokukai-2004-90621A is provided with a jetting quantity measuring device measuring a jetted ink quantity, and is configured to correct the voltage value of a drive signal by multiplying a measured value of the jetting quantity measuring device by a correction coefficient to converge the measured value.
Here, FIG. 10 is a histogram showing the scattering of drop speeds of the ink droplet which is jetted from a single nozzle 100 times by applying a drive signal of a predetermined voltage value to an actuator. As apparent from FIG. 10, there is a case where the jetting speeds scattering ranges ±0.75% from an average speed (the part of 0% in FIG. 10) even if a drive signal of the same voltage value is applied. That is, in the case where a voltage value is corrected by the liquid jetting device of JP-Tokukaihei-7-256884A, the voltage value is corrected by feeding back a jetting speed decreasing in value by 0.5% (a J part in FIG. 10) or a jetting speed increasing in value by 0.75% (a K part in FIG. 10) as the case may be. If a singular value of a small frequency is used for correction, an accurate correction cannot be performed, and the improvement of the image quality cannot be desired as a result.
Moreover, because there is the fluctuation between nozzles mentioned above also in the jetting quantity similarly in the jetting speed, there is the possibility that a value of a small frequency is used for a correction even in the case where a measured value is multiplied by a correction coefficient as in the liquid jetting device of JP-Tokukai-2004-90621A, and there has been a problem of the accuracy of a correction. In particular, in the case where a singular value of a small frequency is used for a correction, the convergence of values takes a long time and further there is a possibility of diverging without converging even if the multiplication of the correction coefficient is performed.